The
Perineum
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•The perineum is
diamond shaped and
is bounded by:
•The symphysis
pubis, the tip of
the coccyx & the
ischial tuberosities,
Sacrotuberous
ligaments.
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•The diamond-shaped perineum is divided by a
broken line into the urogenital triangle and the
anal triangle.
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•The perineal membrane fills the anterior gap in
the pelvic diaphragm (the urogenital hiatus, but is
perforated by the urethra in both sexes and by
the vagina of the female.
•The membrane and the ischiopubic rami provide
a foundation for the erectile bodies of the
external genitalia.
•The midpoint of the line joining the ischial
tuberosities is the central point of the perineum.
The perineal body.
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•In order to avoid its injury during
childbirth an incision should be made
on the wall of the vagina and near by
perineum (episiotomy).
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Anal Triangle
•The anus, or lower opening of the anal canal,
lies in the midline, and on each side is the
ischiorectal fossa.
Anal Canal
•The anal canal is about 4 cm long and passes
downward and backward from the rectal ampulla
to the anus.
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Structure
•The mucous membrane of the upper half of the
anal canal is derived from hindgut endoderm.
•It has the following important anatomic features:
•It is lined by columnar epithelium.
•It is thrown into vertical folds called anal
columns contain terminal branches of
superior rectal vessels).
Site of anastomosis b/n superior rectal
veins of portal system with middle & inferior
rectal veins of the caval system.
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•Superior ends of the anal columns = anorectal
line (point of meeting rectum with anal canal)
•Anal columns are joined together at their lower
ends by small semilunar folds called anal valves.
•The inferior comb-shaped limit of anal valves
forms the pectinate line (dentate line or
mucocutaneous line), & lies immediately below
the anal valves.
The pocket like recess above each anal valve
is termed anal sinus.
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•The pectinate line represents point of junction
b/n embryonic hindgut & an invagination of
embryonic skin, proctodeum.
indicates a dividing line b/n two types of
epithelia & two sources of nerve & arterial
supply; as well as lymphatic & venous drainage.
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Clinical notes
Hemorrhoids
•Internal hemorrhoids
•Are varicosities of the tributaries of the
superior rectal (hemorrhoidal) vein and are
covered by mucous membrane.
•A fold of mucous membrane and submucosa
containing a varicosed tributary of the superior
rectal vein.
•Occur in the upper half of the anal canal,
where the mucous membrane is innervated by
autonomic afferent nerves.
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They are painless
and are sensitive
only to stretch.
•The tributaries of the vein, which lie in
the anal columns at the 3-, 7-, and 11o'clock positions when the patient is
viewed in the lithotomy position.
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•Internal hemorrhoids that prolapse thru the anal
canal are often compressed by the contracted
sphincters, impeding blood flow.
External hemorrhoids
•Are varicosities of the tributaries of the inferior
rectal (hemorrhoidal) vein as they run laterally
from the anal margin.
•External hemorrhoids are covered by the
mucous membrane of the lower half of the
anal canal or the skin, and they are innervated
by the inferior rectal nerves.
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They are sensitive to
pain, temperature,
touch, and pressure,
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Contents of the Male Urogenital Triangle
•In the male, the triangle contains the urethra,
penis and scrotum.
1.Penis
•Has a fixed root and a body that hangs free.
The root
•Is made up of three masses of erectile tissue
called the bulb of the penis and the right and
left crura of the penis.
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Root of penis and perineal muscles
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Root and body of the penis
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•The bulb is situated in the midline and is
attached to the undersurface of the urogenital
diaphragm.
•It is traversed by the urethra and is covered on
its outer surface by the bulbospongiosus
muscles.
•Each crus is attached to the side of the pubic arch
and is covered on its outer surface by the
ischiocavernosus muscle.
•The bulb is continued forward into the body of
the penis and forms the corpus spongiosum.
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•The two crura converge anteriorly and come to
lie side by side in the dorsal part of the body of
the penis, forming the corpora cavernosa.
Body of the Penis
•Composed of three cylinders of erectile tissue
enclosed in a tubular sheath of fascia (Buck's
fascia).
•The erectile tissue is made up of two dorsally
placed corpora cavernosa and a single corpus
spongiosum applied to their ventral surface.
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•At its distal extremity, the
corpus spongiosum expands to
form the glans penis, which
covers the distal ends of the
corpora cavernosa.
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Blood Supply
Arteries:are branches of the internal pudendal
artery.
•The corpora cavernosa are supplied by the
deep arteries of the penis.
•The corpus spongiosum is supplied by the
artery of the bulb.
•In addition, there is the dorsal artery of the
penis.
Veins
•The veins drain into the internal pudendal veins.
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2.Scrotum
•Is an outpouching of the lower part of the
anterior abdominal wall.
•Contains the testes, the epididymis, and the
lower ends of the spermatic cords.
•The wall of the scrotum has the following layers:
•Skin
•Superficial fascia
•External spermatic fascia derived from the
external oblique.
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•Cremasteric fascia derived from the internal
oblique.
•Internal spermatic fascia derived from the
fascia transversalis.
•Tunica vaginalis: which is a closed sac that
covers the anterior, medial, and lateral surfaces
of each testis.
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Arteries
•Anterior scrotal arteries from the external
pudendal arteries.
•Posterior scrotal arteries from the superficial
perineal branches of the internal pudendal
arteries.
•The cremasteric arteries (branches of the
inferior epigastric arteries).
Veins
•The veins accompany the corresponding
arteries
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Lymph Drainage
•The wall of the scrotum is drained into the
medial group of superficial inguinal lymph
nodes.
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Nerve Supply
•The anterior surface of the scrotum is supplied
by the ilioinguinal nerves and the genital
branch of the genitofemoral nerves.
•The posterior surface is supplied by branches
of the perineal nerves and the posterior
cutaneous nerves of the thigh.
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Testes
•They are paired, ovoid male gonads, that have
an elastic consistency.
• Produce spermatozoa.
• Produce a hormone (testostrone) which is
responsible for secondary male sexual
characteristics.
•In adults each testis has a weight of 25 gm and a
length of 4-5cms.
•The testes are suspended in the scrotum by the
spermatic cord.
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•Their posterior margins are covered by the
epididymis and the lower part of the spermatic
cord.
•The right and left testes are separated by a
connective tissue septum called scrotal septum.
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Microscopic structure of the testis
•Each testis is enclosed in the capsule of tunica
albuginia that thickens posteriorly to form the
mediastinum testis from which the septae radiate
to subdivide the testis into lobules.
•Each lobule contains convoluted seminiferous
tubules, the convoluted tubules unite to straight
tubule which open into the rete testis.
•Efferent ductules arise from the rete testis that
transport newly produced sperms to epididimis.
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Blood vessels of the testis
Artery
•Testicular a. from abdominal aorta.
•Inferior vesical artery also supplies the testis.
Vein
• Form the pampiniform plexus that drains
into the testicular veins.
• Right testicular vein drains in to the IVC and
the left into the left renal vein.
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Epididymis
•C-shaped structure on the posterior margin of
testis.
•It stores spermatozoa until they are emitted.
•It consists of 3 parts: head, body and tail.
Head: Upper part formed by efferent ductule
that opens to duct of the epididymis .
Body: Consists of the convuluted duct of
epididymis found behind the testis
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Tail - the lowest part of epididymis.
•The duct is thickened and widened in this part to
form the ductus deferens.
•Blood vessels and lymphatics of the epididymis
are similar to the testis.
Nerves: From hypogastric plexus.
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Spermatic cord
•Is a collection of structures that pass through the
inguinal canal to and from the testis.
•Begins at the deep inguinal ring lateral to the
inferior epigastric artery and ends at the testis.
The structures are as follows:
•Vas deferens
•Testicular artery
•Testicular veins (pampiniform plexus)
•Testicular lymph vessels
•Autonomic nerves
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•Genital branch of the genitofemoral nerve,
which supplies the cremaster muscle.
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Contents of the Female Urogenital Triangle
•In the female, the triangle contains the external
genitalia and the orifices of the urethra and the
vagina.
1.Clitoris
•Corresponds to the penis in the male, is
situated at the apex of the vestibule anteriorly.
•It has a structure similar to the penis.
•The glans of the clitoris is partly hidden by the
prepuce.
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Root of the Clitoris
•Is made up of three masses of erectile tissue called
the bulb of the vestibule and the right and left crura
of the clitoris.
•The bulb of the vestibule corresponds to the bulb of
the penis, but because of the presence of the vagina,
it is divided into two halves.
•It is attached to the undersurface of the urogenital
diaphragm and is covered by the bulbospongiosus
muscles.
•The crura of the clitoris correspond to the crura of
the penis and become the corpora cavernosa
anteriorly.
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•Each remains separate and is covered by an
ischiocavernosus muscle.
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Body of the Clitoris
•Consists of the two corpora cavernosa
covered by their ischiocavernosus muscles.
•The corpus spongiosum of the female is
represented by a small amount of erectile tissue
leading from the vestibular bulbs to the glans.
Glans of the clitoris
•Is a small mass of erectile tissue that caps the
body of the clitoris.
•It is provided with numerous sensory endings.
•The glans is partly hidden by the prepuce.
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Blood Supply
Arteries:are branches of the internal pudendal
artery
•The corpora cavernosa are supplied by the
deep arteries of the clitoris.
•The corpus spongiosum is supplied by the
artery of the bulb.
•In addition, there is the dorsal artery of the
clitoris.
Veins
•The veins drain into the internal pudendal veins.
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• A tubular female organ of copulation, birth
canal and the excretory duct for the products of
menstruation.
7.5 cm long anterior wall, a 9 cm long
posterior wall and a width of 4 cm.
•The recess between the cervix and the walls of
the vagina is called fornix.
–There are four fornices of the vagina:
anterior, posterior and two lateral.
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Extends from cervical canal to exterior.
Layers: Mucosa, muscularis, and adventitia.
The cervix of the uterus pierces its anterior wall.
 The vaginal orifice in a virgin possesses a thin
mucosal fold, called the hymen, which is
perforated at its center.
 The upper half of the vagina lies above the
pelvic floor within the pelvis between the
bladder anteriorly and the rectum posteriorly.
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•The lower half lies within the perineum between
the urethra anteriorly and the anal canal
posteriorly.
Structure
•Astratified squamous epithelium lines the
vagina and the vaginal cervix.
•It contains no glands and is lubricated partly
by cervical mucus and partly by desquamated
vaginal epithelial cells.
•In nulliparous women the vaginal wall is
rugose, but it becomes smoother after
childbirth.
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Supports of the Vagina
Upper third:
•Levatores ani muscles and transverse cervical,
pubocervical, and sacrocervical ligaments
Middle third:
•Urogenital diaphragm
Lower third:
•Perineal body.
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Relations
Anteriorly:
•The base of the bladder and the urethra (which
is embedded in the anterior vaginal wall).
Posteriorly:
•The anal canal (separated by the perineal
body), the rectum and then the peritoneum of
the pouch of Douglas which covers the upper
quarter of the posterior vaginal wall.
Laterally:
•Levator ani, pelvic fascia and the ureters, which
lie immediately above the lateral fornices.
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•Four muscles compress the vagina and act as
sphincters:
•Pubovaginalis.
•External urethral
sphincter.
•Urethrovaginal
sphincter.
•Bulbospongiosus.
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Blood Supply
Arteries
•The vaginal artery, a branch of the internal
iliac artery, and the vaginal branch of the
uterine artery supply the vagina.
Veins
•Vaginal veins drain into the internal iliac veins.
Lymph Drainage
•Upper third: Internal and external iliac nodes
•Middle third: Internal iliac nodes
•Lower third: Superficial inguinal nodes
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Nerve Supply
•The vagina is
supplied by
nerves from the
inferior
hypogastric
plexuses.
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The vulva(pudendum)
– Is the term applied to the female external
genitalia.
Consists of:
The labia majora
–Are the prominent hair-bearing folds
extending back from the mons pubis to meet
posteriorly in the midline of the perineum.
–They are the equivalent of the male scrotum.
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The labia minora
•Lie between the labia majora as lips of soft
skin which meet posteriorly in a sharp fold, the
fourchette.
•Anteriorly, they split to enclose the clitoris,
forming an anterior prepuce and posterior
frenulum.
The vestibule
•Is the area enclosed by the labia minora and
contains the urethral orifice(which lies
immediately behind the clitoris) and the
vaginal orifice.
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•The vaginal orifice is guarded in the virgin by a
thin mucosal fold, the hymen, which is perforated
to allow the egress of the menses.
•May have an annular, semilunar, septate or
cribriform appearance.
•Rarely, it is imperforate and menstrual blood
distends the vagina (haematocolpos).
•At first coitus the hymen tears, and after
childbirth nothing is left of it but a few tags
termed carunculae myrti formes.
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Blood Supply
•Branches of the external and internal
pudendal arteries on each side
Nerve Supply
•The anterior parts of the vulva are supplied by
the ilioinguinal nerves and the genital branch
of the genitofemoral nerves.
•The posterior parts of the vulva are supplied
by the branches of the perineal nerves and the
posterior cutaneous nerves of the thigh.
Lymph Drainage
•Medial group of superficial inguinal nodes
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